SVN_SILENT made messages (.desktop file)
sorting: remember the sort direction

The sort direction (ascending/descending) should be saved even in cases we're
asked to "sort" an empty mailbox.
Reapply threading/sorting/searching after model gets reset

Previously, we would only do this when threading was active. This change makes
sure that we also respect the sort direction after the mailbox changes.

BUG: 333198
Ubuntu: refactor how we ask for the descending sort

There's no need to repeat this sorting preference all the time anymore.